PSI - Issue 25

Francesco Leoni et al. / Procedia Structural Integrity 25 (2020) 348–354 Francesco Leoni / Structural Integrity Procedia 00 (2019) 000–000

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Figure 6: SEM fractograph of tensile specimen tested at 500 °C.

Conclusions Tensile properties of a 1.4 mm diameter filler wire of the AA6082 type being used in the HYB process have been investigated at five different temperatures from room temperature and up to 500 °C. The following conclusions can be drawn from the investigation:  At room temperature the tensile strength of the filler wire is very high. At the same time as the ductility is correspondingly low. This is due to the fact that the wire has been cold-drawn down to its final diameter of 1.4 mm prior to tensile testing;  The tensile strength of the filler wire decreases with increasing temperatures. The softening starts already at very low temperatures and the strength continues to drop within the entire range examined;  Necking in combination with considerable dimple formation across the fracture surface are observed at all temperatures up to 350 °C, showing that the tensile ductility of the AA6082 filler wire is satisfactory. The tendency to necking and dimple formation becomes more pronounced with increasing temperatures.  When the temperature is raised to 500 °C the fracture mode becomes completely different, indicating a change in the failure mechanism. At this temperature necking is no longer noticeable. At the same time the fracture surface appears rough, probably because intergranular slip and grain boundary sliding become predominant at high temperatures, which, in turn, promote separation between grain boundaries when the material is subjected to tensile stress. This type of failure, being associated with negligible necking and intergranular slip, is typical of creep rupture. Acknowledgements The authors acknowledge the financial support from HyBond AS, NTNU and NAPIC (NTNU Aluminium Product Innovation Center). The authors would also like to thank Carl-Magnus Midtbø for his help and assistance with the tensile testing.

References

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